Christmas rail works: 'Plans in place' to stop repeat of last year
Rail passengers facing disruption over the festive period have been promised measures are in place to stop a repeat of last year when overrunning work left thousands stranded.
Great Western services between Slough and London Paddington will be closed on 27 and 28 December to allow for major work as part of the Crossrail project.
High-speed trains through Reading will be diverted into London Waterloo.
Last year Network Rail failed to finish on time, leading to travel chaos.
Heathrow Connect and Heathrow Express services will also be cancelled on 27 and 28 December as part of "essential improvements"
Network Rail advised anyone planning to travel over this period to first check online for service disruptions.
Nick Mann, from Network Rail, said: "We absolutely understand the impact overrunning engineering works has on passengers, we got it wrong last year and we apologised at the time.
"We've been planning for these works in meticulous amounts of detail for well over 12 months now to make sure we get it right."
Revised timetables will be in operation from 29 December to 3 January.
Analysis, Paul Clifton, BBC South Transport Correspondent
The biggest single bit of these works is replacing a junction at Heathrow Airport - this is all about preparing for the arrival of Crossrail.
Some local services will be replaced by buses, some longer distance services through Reading will be diverted down to Basingstoke and up to Waterloo - that will add about an hour to the journey.
Services coming in from Bristol will divert off at Oxford, go up to Banbury and then go all the way down to London Marylebone station.
Let's remember what happened last year - engineers did not hand back the tracks on time nor did they warn the train companies and the result was chaos.
Network Rail was hauled up before a committee of MPs and given a severe dressing down, so fingers crossed this year.